Driving assessment for maintaining mobility and safety in drivers with dementia: Cochrane systematic review

Abstract

Assessed as up to date: 2013/03/12

Background

Demographic changes are leading to an increase in the number of older drivers: as dementia is an age-related disease, there is also an increase in the numbers of drivers with dementia. Dementia can impact on both the mobility and safety of drivers, and the impact of formal assessment of driving is unknown in terms of either mobility or safety. Those involved in assessment of older drivers need to be aware of the evidence of positive and negative effects of driving assessment. Cognitive tests are felt by some authors to have poor face and construct validity for assessing driving performance; extrapolating from values in one large-scale prospective cohort study, the cognitive test that most strongly predicted future crashes would, if used as a screening tool, potentially prevent six crashes per 1000 people over 65 years of age screened, but at the price of stopping the driving of 121 people who would not have had a crash.

Objectives

Primary objectives: 1. to assess whether driving assessment facilitates continued driving in people with dementia; 2. to assess whether driving assessment reduces accidents in people with dementia.

Secondary objective: 1. to assess the quality of research on assessment of drivers with dementia.

Search methods

ALOIS, the Cochrane Dementia Group's Specialized Register was searched on 13 September 2012 using the terms: driving or driver* or "motor vehicle*" or "car accident*" or "traffic accident*" or automobile* or traffic. This register contains records from major healthcare databases, ongoing trial databases and grey literature sources and is updated regularly.

Selection criteria

We sought randomised controlled trials prospectively evaluating drivers with dementia for outcomes such as transport mobility, driving cessation or motor vehicle accidents following driving assessment.

Data collection and analysis

Each review author retrieved studies and assessed for primary and secondary outcomes, study design and study quality.

Main results

No studies were found that met the inclusion criteria. A description and discussion of the driving literature relating to assessment of drivers with dementia relating to the primary objectives is presented.

Authors' conclusions

In an area with considerable public health impact for drivers with dementia and other road users, the available literature fails to demonstrate the benefit of driver assessment for either preserving transport mobility or reducing motor vehicle accidents. Driving legislation and recommendations from medical practitioners requires further research that addresses these outcomes in order to provide the best outcomes for both drivers with dementia and the general public.

Author(s)

Martin Alan J, Marottoli Richard, O'Neill Desmond

Summary

Driving assessment for maintaining mobility and safety in drivers with dementia

The proportion of older people in the world is increasing and consequently the number of older drivers is also on the rise. Older people commonly depend upon private motor vehicles for their transport needs and so assessment of older drivers with cognitive impairment is becoming increasingly important. We have reviewed the literature on driving assessment in people with dementia for two reasons. First, we wished to see if assessment helped people with dementia and good driving skills continue driving. Second, we wished to discover whether assessment was useful in preventing road traffic accidents.

Although many authors have studied the motor skills, neuropsychological performance and driving behaviour of drivers with dementia, we found no study that randomised drivers to evaluate these outcomes prospectively following assessment. This highlights the need for caution in applying the literature on driving assessment to clinical settings as no benefit has yet been prospectively demonstrated. It also indicates the need for prospective evaluation of new and existing models of driver assessment to best preserve transport mobility and minimise road traffic accidents.

Reviewer's Conclusions

Implications for practice

There is no randomised evidence to indicate whether neuropsychological, on-road or other assessments of driving ability can help support safe drivers to remain mobile, or to reduce crashes.

Implications for research

More work is required to identify the optimal assessment strategy to help preserve transport mobility. A key challenge here is the development of a concise measure of transportation resources and quality, as suggested by Metz 2004.

Screening appears to discriminate unfairly against older drivers and yet in a population who appear to have declining driving skills there is understandable concern about crash risk. Further research is required to develop assessment tools that can reliably identify unsafe drivers with dementia in an office-based setting. Behavioural models may be of benefit here.

RCTs of driving assessment should involve a careful design, randomising people who drive to either formal testing or usual care and assessment, with longitudinal follow-up of satisfaction with transport (Rosenbloom 2003) and crashes or violations. Ethically, this may not pose a public health hazard in view of some memory clinic studies that suggest no increase in crashes in those with dementia (Drachman 1993; Trobe 1996; Carr 2000). Due care will need to be given to advice to participating drivers on informing driver licensing authorities and insurance companies, depending on the jurisdiction(s) within which the study is taking place. The study should also incorporate regular data review by an independent safety committee. As it is clearly undesirable that all drivers with dementia continue driving indefinitely, the use of a measure of transport efficacy, such as the Life Space Questionnaire (Stalvey 1999). may be a better guide to the primary question posed. It is likely that a close monitoring of the study for adverse events would be the best guide to the potential hazards, as, given that crashes are infrequent events, a study based purely on the secondary objective of safety would have to be very large. Extrapolating from Staplin 2003 where 111 out of 1876 participants in the License Renewal Sample crashed in the 20 months' follow-up, giving a crash rate of 0.06 per person over 20 months. Using JMP statistical software (SAS Institute) we estimate that a sample size of 5293 in each group would be required to have an 80% power to detect a 20% difference in crash rate between an unselected older driver population and a dementia group in the same time frame. If, however, we were to choose a larger estimate of increased crash risk such as a 50% difference in crash rates, our required sample size would be 953 per group. For the primary research objective of continued driving, cessation over a 23-month period was almost 50% in a Canadian study of 200 drivers with dementia (Herrmann 2006), giving a withdrawal rate of 0.485 per person over a 23-month period. This would give us a sample size of 2625 in each group to have an 80% power to detect a 10% difference in driving cessation. 

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